Ceramic materials and, in particular, ceramic materials for use in lithium ion battery cathodes, have been an intriguing research field for many years. Out of various ceramic materials suitable for use as lithium ion battery cathodes, lithium transition metal oxides stand out as the most successful category of such cathode material. The crystal structures of lithium transition metal oxides can be a layered structure with a chemical formula of LiMO2 (M: Mn, Co, and Ni, etc.) and a three dimensional spinel structure with a typical chemical formula of LiM2O4 (M: Mn). Both the layered structure and the spinel structure are built up by transition metal and oxygen to form the framework, among which the lithium ions are intercalated.
Conventional methods for ceramic material preparation generally can be summarized as solid-state chemistry, co-precipitation, hydrothermal, sol-gel, and spray-drying. The conventional solid-state chemistry method has several disadvantages, including non-homogeneity, irregular morphology, larger particle size, broader particle size distribution, and poor control of stoichiometry. Thus, insufficient oxidization often occurs, resulting in an imperfect crystal structure that needs repeated calcinations to eliminate the imperfections. To overcome these drawbacks, improved methods, including co-precipitation, hydrothermal and spray-drying methods have been developed. However, these improved methods require either sophisticated and precise chemical reaction procedure control or complicated process and expensive equipment. Also these improved methods may cause environmental problem due to waste generated during the process. In addition to the above methods, sol-gel methods apparently offer a relatively simple and facile method, which either does not cause or causes fewer environmental problems. However, currently known sol-gel methods require a step to drive off the water in the solution at relatively high temperature, in order to achieve the gel state. This driving off of water is actually a concentrating step, needed to achieve a high concentration of solids, so that the resulting mixture will easily turn into a gel upon heating. One major drawback is that, during this step, phase separation among different components is quite possible, even likely, and this results in various non-homogeneities from this procedure. The non-homogeneities may present as one or more of irregular element distribution, irregular morphology, irregular and/or broad particle size distribution and irregular, non-uniform stoichiometry, which stoichiometric problems are especially serious for dopants. Such non-homogeneities can result in a need for additional processing and/or production of inferior ceramic products.
Thus, there has remained in the art a strong need for solving the problems of non-homogeneity, irregular morphology, larger particle size, broader particle size distribution, and poor control of stoichiometry, which have plagued the ceramic materials art for many years.